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#1
08-14-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 343 Threads: 127 Thanked 525 Times in 192 Posts Reputation: 535
Composition of the double stranded product

A 3 year old boy is diagnosed with MCAD (medium chain acyl-CoA dehydrogenase ) deficiency and sample of DNA is obtained.
The base composition of one strand is analyzed and found to contain
A = 10
C = 12
G = 15
T = 8
What is composition of double stranded product

a) A=27 C=20 G=27 T=20
b) A=22 C=33 G=23 T=23
c) A=20 C=24 G=24 T=20
d) A=18 C=27 G=15 T=18
e) A=08 C=12 G=15 T=10
 The above post was thanked by: dr_lizard (09-06-2011), usluipek (08-14-2011), usmleman2020 (08-15-2011)

#2
08-14-2011
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#3
08-14-2011
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shouldn't it be A = 18 C= 27 G =27 T =18 ?

#4
08-14-2011
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#5
08-14-2011
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the ans is C in a double stranded DNA
A=T
C=G
#6
08-15-2011
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Ccccccccccccccccc
#7
08-15-2011
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Quote:
 Originally Posted by patient doctor shouldn't it be A = 18 C= 27 G =27 T =18 ? please explain
Agree with you.
#8
08-15-2011
 USMLE Forums Addict Steps History: 1+CK+CS Posts: 115 Threads: 3 Thanked 267 Times in 41 Posts Reputation: 277

A = 10 T=10
C = 12 G=12
G = 15 C=15
T = 8 A=8
What is composition of double stranded product

a) A=27 C=20 G=27 T=20
b) A=22 C=33 G=23 T=23
c) A=20 C=24 G=24 T=20
d) A=18 C=27 G=15 T=18 (G should be 27)
e) A=08 C=12 G=15 T=10
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#9
08-15-2011
 USMLE Forums Master Steps History: Step 1 Only Posts: 567 Threads: 25 Thanked 524 Times in 263 Posts Reputation: 534

Quote:
 Originally Posted by IKR123 A 3 year old boy is diagnosed with MCAD (medium chain acyl-CoA dehydrogenase ) deficiency and sample of DNA is obtained. The base composition of one strand is analyzed and found to contain A = 10 C = 12 G = 15 T = 8 What is composition of double stranded product a) A=27 C=20 G=27 T=20 b) A=22 C=33 G=23 T=23 c) A=20 C=24 G=24 T=20 d) A=18 C=27 G=15 T=18 e) A=08 C=12 G=15 T=10
Should be Answer C is the most reasonable to me, based on the Double Stranded Composition.

As we can see A = T = ( Hydrogen bonds )
G=C 24

Answer E is just the complementary strand for the single stranded DNA.
#10
04-04-2012
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so whats the answer and explanation???
#11
04-04-2012
 USMLE Forums Addict Steps History: Not yet Posts: 183 Threads: 79 Thanked 17 Times in 13 Posts Reputation: 27

shouldnt it be
A=18 T=18 C=27 G=27?
#12
04-04-2012
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agreed, answer is d) and G should be 27 (they forgot to add the complementary 12)

 Tags Molecular-Biology-, Step-1-Questions

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